English
If φ kills all polynomials of natDegree < k and maps monomials to degrees fu(n) with fu shifted, then (φ p).natDegree = fu(p.natDegree).
Русский
Если φ обнуляет все полиномы c natDegree < k и переводит мономы в степени fu(n) с поправкой, тогда natDegree(φ(p)) = fu(natDegree p).
LaTeX
$$$ (\\phi p).natDegree = fu(p.natDegree) $$$
Lean4
@[simp]
theorem eval₂_at_zero : p.eval₂ f 0 = f (coeff p 0) := by
simp +contextual only [eval₂_eq_sum, zero_pow_eq, mul_ite, mul_zero, mul_one, sum, Classical.not_not, mem_support_iff,
sum_ite_eq', ite_eq_left_iff, RingHom.map_zero, imp_true_iff]